Compound thermostatic bulb



Feb. 15, 1944. P. F. K. ERBGUTH 2,341,765

COMPOUND THERMOSTATIC BULB Filed Nov. 2a, 1940 WITNESS. 1 .ENTOR.

PAUL FTK. ERBGUTH 41% (Qu flax BY Patented Feb. 15, 1944 iUNlTED STATES PATENT OFFICTE COMPOUND THERMOSTATIC BULB Paul F. K. Erbguth, Brooklyn, N. Y., assignor to Charles J. Tagliabue Mfg. 00., Brooklyn, N. Y., a corporation of New York Application November 26, 1940, Serial No. 367,252

' Claims.

This invention generally relates to improvements in thermostatic bulbs and their method of manufacture, particularly where a plurality oi devices are to be operated in response to changes 01' temperature at a single point or location.

This problem ordinarily arises where both an indicator and a controller for the temperature are needed in processing a fluid Or other substance. One solution consists of a socket well which is screwed into the wall of the pipe and contains separate bulbs for respectively actuating the measuring and the controlling devices. Such an arrangement has been found to cause too slow a response of either or both devices and to be objectionably bulky.

A primary object of the invention i to provide a compound bulb which causes a minimum of lag. A related object is to reduce the diameter and weight of such bulb to a minimum. A further object is the provision of an arrangement that is rugged and hence safe from damage due to the impact of relatively heavy material carried by a flozving fluid when the bulb is installed in a condu t.

A particular object is the provision of a unitary 0r compound bulb for the actuation of two separate tube systems. y

These and other object of my invention will appear to those skilled in the art from the accompanying drawing and specification, in which are illustrated and described several embodiments of the invention, it being my intention to claim all that I have disclosed which is new and useful.

In the drawing, Fig. 1 shows the preferred embodiment of a compound bulb without a socket generally in longitudinal section and diagrammatically shows two separate tube systems which are actuated in accordance with the temperature of the bulb. A socket may be used when it is necessary to provide a pressure-tight well from "which the compound bulb is readily removable as,

e. g., checking or the maintenance of the measuring or the controlling device. Fig. 2 is an inverted plan view, partially in section, of an alternative arrangement of the compound bulb unit in-which the two bulbs are parallel and adjacent. The section is taken between the ends of the bulbs. The compound bulb obviously may beattached, however, directly to an insulated wall in any convenient manner and its outer surface exposed to the fluid or material the temperature of which is being measured.

In Fig. 1, the compound bulb I is attached to wall 2 of a pressure chamber which contains the trolling lnstrument 6 which pneumatically, e. g..

governs a control valve I for steam or other heating fluid a usual.

Bulb 3 preferably contains a. liquid 8 such as butane or ether which has a suitable vapor pressure for actuating the capsule 5 at the controlling temperature which is, e. g., around 144 F. for pasteurizing milk. The upper bulb 9 is connected by tubing Ill with bourdon II in meter l2 which may be either an indicator or a recorder. Bulb 9 preferably contains another liquid l3 such as methyl chloride which has a range of vapor pressures suitable for, e. g., from 30-220 F. Instead of using vapor pressures which correspond with the value of the sensed temperature, gas or liquid expansion may be used within this invention. The use of vapor pressure has an obvious advantage in controlling within any fixed small range of temperatures since the liquid can be selected which is most suitable for such range. With the liquids stated above, the upper bulb is preferably made at least as large as the lower bulb so that the upper bulb has adequate capacity for all of the liquid in its tube system when the temperature measured falls below that of the bourdon l I and the tubing III which is exposed to room temperature. The controlling tube system does not have to meet this requirement if all of the controlling range is above the highest temperature in the room, as it i in the present case. The modifications necessary to take care of different positions for both vapor pressin'e and other types of tube systems are well known to any one skilled in the art and form no part of the present invention, any arrangement shownas to this feature being shown only by way of example.

The lower bulb has its upper end swaged down to nearly the size of the tubing 4 which is inserted within the swaged end and welded to it to seal the lower bulb. The upper bulb 9 has its upper end swaged down and is slipped over the tubing 4 and its lower end is slipped over the swaged upper end of the lower bulb and welded to the junction of the swaged portion with the fulldiameter portion of the lower bulb to seal the lower end oi. bulb 9. Tubing I0 is inserted through the reduced upper end of bulb 9. The upper bulb has its upper end soldered or welded tight around both tubings l and I ll.

Coupling section I4 is slipped over both tubings l and I0 and the swaged upper end bulb 9 and has its lower end welded tothe outside or the upper portion of bulb I. The entire outside surface of this unit is preferably ground smooth so that it appears to be a single piece of metal.

This metal is preferably stainless steel or monel Further, some more readily detachable design of attachment may be used under the invention for a milk pasteurizer which is mentioned elsewhere I herein also by way of example.

As is customary, the upper end of coupling H has a protecting semi-flexible tubing l8 attached to it;

The embodiment of Fig. 2 has two like bulbs 3 and- 9' located parallel and beside each other. They are joined by welding to flll up the hollows between them and they are likewise threaded into coupling section H and the openings sealed by welding. The external surface is then finished to be continuous and readily cleanable. The bulbs are filled as described with respect to the preferred embodiment.

The alternative embodiment of Fig. 2 also has a 'quick response and retains the advantage of a unitary connection. It additionally is stiffer in one transverse direction than the longer unit of Fig. 1 and hence is suited for exposure to a high-velocity transverse stream. Since unit I is'shorter than is unit I, it will fit into spaces, e. g. in a small pasteurizing chamber, in which there is not suificient room available for thelonger unit of Fig. 1. While the welding method of construction has the considerable advantage of using like bulbs 3 and 9', still under the invention the compound bulb unit may be formed from a single bar of metal by drilling and machining, and may be useful in special processes where any difference of the material at the surface may be objectionable even though it be not visible. A thinner wall may be used for the controlling bulb than for the metering bulb to give a quicker response. Also, the controlling bulb can be located on the upstream side where there is a transverse flow to obtain this desirable eflect.

In operation, both bulbs are quickly responsive to temperature changes since thereis only a single metal wall between the fiuid whose temperature is being measured and the temperature-sensitive liquid in the bulb and because there is relatively large surface area of the bulb per unit of bulb volume on account of its elongated cylindrical shape which is far from the spherical shape which has the smallest ratio of surface area to volume. The small diameter of bulb which results from the tandem arrangement is also highly desirable and even essential for certain installations as in a pipe in which the unit is readily inserted in any line at an elbow with the axis of the unit concentric with that of the pipe.

Another effect of the use of a minimum diameter of bulb is that there is a minimum deformation due to external pressure, an eifect which is negligible with vapor tension tube systems but not with liquid or gas expansion systems. The

lower bulb in the device of Fig. 1 is preferably used for controlling since it. is separated from the wall by the upper bulb and hence provides a prompter sensing of a temperature which varies in a lively manner. In processing fluids, the control is normally more important than the measurement because it is the accuracy of the control that generally determines the value of the prod-, uct eventhough the recorded measurement be used as the criterion. In view of the intimate thermal connection between the two bulbs, their temperature will be very close in most cases in practice.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, butrecognize that various modifications are possible within the scope of the invention claimed. Where a "physical condition" of a fluid occurs in the claims it refers to a. condition of the class which includes pressure and density (or specific volume) and corresponds with the temperature of the fluid, the choice being a matter of convenience since upon an increase of the temperature, the pressure rises if the volume be held constant, the volume increases if the pressure be held constant, or both can increase simultaneously or one can increase while the other decreases, depending upon the design of the fluid-containing system. Also where a welded connection between metal parts is used in the claims, this means any contact with said metal parts and, upon cooling, to

re-solidify to join the parts in a connection which is rigid mechanically and of high thermal conductivity, this class including, e. g., welding per se, brazing and soldering.

I claim:

1. A compound rod-shaped thermal bulb unit comprising, in combination, two slender generally cylindrical fluid-containing metal bulbs of substantially the same external diameter with one bulb having one end closed and its other and reduced in diameter to fit as a male part within a portion of the cylinder of the other bulb which acts as its mating female part, a cylindrical metal sleeve having substantially the same external diameter as that of said bulbs, the other end of said other bulb being reduced in diameter to fit as a male part within a mating portion of the cylindrical sleeve which acts as its mating female part, and two seals at least filling any gaps between the ends of said female parts and the generally frusto-conical reducing transitions on said male parts of the stated couplings, the outer surface of at least both bulbs being finished to form named bulb and both of said tubes being arranged to pass through the reduced end of said other bulb; and two seals with one seal bonding the metal of the reduced diameter end of the first named bulb with the metal wall of its tube to make such bulb bottle-tight except for the hole in its tube and the other seal bonding the outlet of said other end of saidother bulb with the metal walls of both said tubes to make such bulb bulb which is operatively connected to the other of said instruments and of substantially the same external diameter as that of said first bulb, and two bottle-tight seals mechanically and thermally connecting said second bulb respectively with said first bulb and said cylinder to have the axes of said bulbs and of said cylinder substantially in alignment, one of the stated connections of said second bulb including a coupling composed of portions of the stated cylindrical elements in which the female part has its external diameter unchanged from that of the stated bulbs and sleeve elements, the male part has its external diameter reduced from said diameter to less than the internal diameter of the female part which sheaths the male part, and its said bottletight seal comprises a seal ng material of high heat conductivity at least filling any gap between the end of the female part and a generally frustcconical transition between said full and reduced external diameter portions of the male part and said seal being finished to have the same external diameter as that of said bulbs and cylinder.

3. In a system having two instruments of the class for measuring or controlling the temperature in a vessel for a fluid, a compound bulb rodshaped unit which comprises, in combination, a first slender, cylindrical metal bulb which is operatively connected to one of said instruments, a

cylindrical sleeve of substantially the same external diameter as that of said bulb and constructed to enable the unit to be removably attached to said vessel, a second slender cylindrical bulb which is operatively connected to the other of said instruments and substantially the same external diameter as that of said first bulb, and two bottle-tight seals mechanically and thermally connecting said second bulb respectively with said first bulb and said cylinder to have the axes of said bulbs and of said cylinder substantially in alignment, one of the stated connections of said second bulb including a coupling composed of portions of the stated cylindrical elements in which the female part has its external diameter unchanged from that of the stated bulbs andsleeve elements, the male part has its external diameter reduced from said diameter to less than the internal diameter of the female part which sheaths the male portion, and its said bottletight seal at least fills any gap between the end of the female part and a generally frusto-conlcal transition between said full and reduced external diameter portions of the male part, and said seal has the same external diameter as that of said bulbs and cylinder.

4. A compound thermal bulb unit comprising two elongated tubes and three substantially cylindrical members having substantially the same external diameter and connected together in endwise fashion so that all three members form a rod-shaped unitary whole and provide three substantially cylindrically-shaped chambers whose central axes extend lengthwise of the unit, said tubes both extending through the chamber of one of said members and each of said tubes extending through an end wall of one of the two other members into communication with the chamber thereof, said two other members each being fluid-tight except for the passage through its associated tube and containing in its chamber a temperature-sensitive fluid, the tubepenetrated wall intermediate said two other members forming a common wall between the chambers of such two members and the tube penetrating said common wall extending entirely through the chamber of one of said members and being exposed on its exterior to the pressure of the fluid in such chamber and being exposed on its interior to the pressure of the fluid in the chamber of the other of said members.

5. A compound thermal bulb unit comprising two elongated tubes and two members having substantially the same external dimensions and connected together in endwise fashion to form a rod-shaped unit, said members being formed to provide two elongated chambers whose central axes extend lengthwise of the unit, said tubes both extending throughone end wall of such rodshaped unit, one of said tubes being in communication with the chamber of the member formed in part by such end wall and the other of said tubes extending entirely through such chamber and through an end wall of the other member into communication with the chamber thereof, said two members each being fluid-tight except for the passage through its associated tube and containing in its chamber a temperaturesensitive fluid, the tube-penetrated wall intermediate said two members forming a common wall between the chambers of such two members and the tube penetrating said common wall and extending entirely through the first-mentioned chamber, being exposed on its exterior to the pressure of the fluid in such chamber and being exposed on its interior to the pressure of the fluid in the chamber of the other of said members, and means for mounting said members on a support.

PAUL F. K. ERBGUTH. 

